Hitherto, among spark plugs, there are spark plugs including a noble metal chip that is provided on a center electrode and a noble metal chip that is provided on a ground electrode (See German Patent Application Laid-Open No. 102011077279). When, in such spark plugs, spark discharge is repeatedly performed between the electrodes provided with the noble metal chips, a discharge surface of the noble metal chip of the center electrode and a discharge surface of the noble metal chip of the ground electrode are worn. This causes a gap formed between the center electrode and the ground electrode to be enlarged, as a result of which it is no longer possible to stably generate sparks.
Accordingly, a technology for suppressing wearing of a noble metal chip of a ground electrode as a result of enlarging a discharge surface by increasing the diameter of the noble metal chip of the ground electrode exists (See Japanese Patent Application Laid-Open No. 2002-313524).